During the course of spine fusion surgery, bone from spinous processes, laminae, facets and/or iliac crest are removed from a patient and are often reimplanted as autograft in increasingly numerous ways, typically to promote fusion of or other repairs to the patient's bones. In order to achieve bone fusion or osteogenesis, there will desirably be a bone to bone contact surface between the host bone and the bone graft. To achieve such a contact surface, soft tissue normally found on bone, such as periosteum, tendon, muscle, ligament and fibrous tissue will be removed from the contact point of both the host and graft bone. It has been well documented in the clinical literature that that intervening soft tissue hinders, if not totally prevents the connection of bone cells. Such impedance or prevention of the passage of the bone cells may cause the fusion procedure to fail thereby resulting in a negative impact on the health of the patient. One well known complication of spine fusion surgery is pseudoarthrosis, which can occur when a patient's vertebral segments fail to fuse together in a desired manner, often leading to back pain, instability, and need for further surgery. Even if a given fusion procedure is successful, the process may take a year or more for completion, and during this time (or for varying periods afterwards) the patient often experiences resultant pain and disability. There are many expensive methods, devices, biologics, and allografts currently commercially available that claim to improve the rate and/or quality of fusion in a surgical procedure.
Autologous bone graft refers to the removal of bone from one location in a patient and subsequently placed in the same and/or another location in the same patient. This type of bone graft is commonly called an autograft, and one major factor contributing to a successful and rapid fusion using autograft is “bone quality.” The quality of bone that is prepared, removed, processed and reimplanted as autograft is often highly dependent on the techniques and experience of an individual surgeon, as well as the surgical technologist's skill level. Before bone can be reimplanted into a patient, the surgeon or surgical technologist will desirably clean the bone of connective tissues, and prepare the bone for fusion in various ways. Current methods of cleaning of the bone prior to reimplantation can include manually scraping the bone with various periosteal elevators, curettes, rongeurs, cautery tools and other multi-purpose tools. Typically, the muscles are stripped away from the bone using cautery and Cobb elevators. Soft tissue is partially removed with large rongeurs, and various portions of the bone are curetted. Depending upon the type of surgical procedure and type of surgical access (i.e., open, less-invasive and/or minimally-invasive approach paths), the spinous processes may be cut and the cut bone given to an assistant or technologist. Similarly, laminae and/or facets can be drilled (often with significant loss of bone stock) and may be rongeured, with small bone pieces given to the technologist, who may proceed to use fine rongeurs to remove any remaining soft tissue from the saved bone. This type of bone preparation and cleaning can be a tedious and time-consuming process. Prior to reimplantation, the harvested bone is then cut into small pieces, either manually with rongeurs, or mechanically (i.e., with a bone mill).
In many cases, the current bone cleaning process is often, tedious, difficult, incomplete, and/or time consuming resulting in (1) incomplete or inadequate bone graft preparation that may lead to delayed and inadequate fusion or healing, (2) incomplete or inadequate bone bed preparation that may lead to delayed and inadequate fusion or healing, (3) the use of undesirable bone graft, especially where it incorporates and/or is utilized with attached small tissue, (4) the discarding of good bone stock because it is difficult or impossible to separate from associated soft tissue, (5) an increase in the occurrence of pseudoarthrosis, or (6) failure of the surgical procedure. In all cases, these results may be suboptimal.
To compound the existing problems described above, the surgeons and/or surgical technologists typically use a combination of general purpose or various other cutting tools to prepare and remove autograft tissues. The tools that are typically used can include general multi-purpose tools that may be designed for proper bone removal, but are not intended and/or well suited to remove soft tissue. Such general multi-purpose tools can include rongeurs, curettes, periosteal elevators, drill bits, burrs and other tools. For example, currently used drill bits and burrs could be used to clean bone, but these are designed to cut, ream, or grind away bone, and are not typically intended to remove soft tissues while maintaining optimal fusion bone yield. Using generalized multi-purpose tools to prepare and remove the autograft can yield a wide variety of disadvantages, including (1) low autograft bone yield, (2) disposal of bone autograft because the bone graft may be too strongly attached to connective tissue for adequate or timely removal for the operation, (3) poor tool strength and material/bone build-up because it may not be used for its intended purpose, (4) multiple tool exchanges (and additional time for the surgeon) be may be required to accomplish preparation of a given anatomical structure of the patient, (5) loss and/or contamination of useable bone material where tool linkages, lubricants and/or coolants prevent collection and utilization of removed material, (6) difficulty in collecting removed bone material from cutting surfaces and/or tool voids, and/or (7) loss of bone from mishandling during the course of cleaning the bone.
Pre-existing devices for denuding, decorticating and shaping bone generally incorporated one of six basic design elements; fluted bone burrs, saw blades with various tooth configurations, bone cutting rongeurs, scalpels, cautery devices and wire-bristle type brushes. While some such instruments have been used to remove soft tissue and shape bone, each is functionally limited in providing an effective means to remove soft tissue from bone.
As an example of prior art, bone burrs have been commonly used to decorticate autografts and allografts. However, to remove soft tissue from bone, bone burrs require significant force and high speed rotation of the burr. The force applied, as well as the high speed rotation of the burr, typically generates heat at the contact point where the burr is placed on the bone. Such heat increases the potential for the onset of thermal necrosis. Additionally, such prior art devices commonly require the application of water during its use to reduce the heat build-up. The use of water can significantly decrease the visibility within the operative area and thereby creates a potential surgical problem.
An earlier prior art device, the bone saw blade, was designed to cut bone in a straight line. Though the saw blade can effectively cut bone, it is ineffective and impractical to use a saw blade to remove layers of soft tissue from bone, as the saw is typically unable to differentiate between the types of tissue(s) it is cutting. Attempts at such removal generally resulted in loss of bone stock and very little removal of the soft tissue. Further, the use of saw blades does not provide a means to easily contour round bone or bone grafts.
An example of a prior art manual instrument device is represented by the bone cutting rongeur. This instrument can be used to remove soft tissue from bone and has been used for this purpose. Such use however, requires that the jaws of the device bite into the bone itself and thereby typically remove bone material in the process of removing soft tissue. The use of such a device is both time consuming and ineffective when small autograft or allograft are being used, and it is difficult to follow the contours or curved surfaces with rongeurs. Additionally, when bone cutting rongeurs are used, the volume of bone loss is significantly higher than with the current invention.
While not designed for use as a soft tissue removal device, the electro-cautery device can remove soft tissue as it effectively burns soft tissue away from bone. However, this device creates a significant amount of heat at the contact point of the cautery tip on the bone. Such large amounts of heat generation increase the potential of terminal necrosis at the bone contact point. Prior art devices used to remove soft tissue, decorticate and or shape bone, do not allow sufficient control of the amount of soft tissue removed as compared to the amount of bone removed or the device creates significant heat at the bone/device interface, thereby increasing the potential for a negative clinical result.
Another prior art device for soft tissue removal includes a wire-bristle type rotary cutter, such as disclosed in U.S. Pat. No. 5,733,288, the disclosure of which is incorporated herein by reference in its entirety. While wire-bristle rotary cutters are disclosed as being capable of separating soft tissue from underlying bone, the wire bristles will often very quickly fatigue and fracture in contact with the underlying bone surface, potentially ejecting the fractured wire outward in a manner which makes such brushes highly undesirable for use in surgical procedures. Moreover, the bristles can also easily remove hard and/or bony tissues in an indiscriminate manner, which is undesired in many instances. In addition, the high rotational speed of wire-bristle rotary cutters can easily generate excessive heat on the bone surface, and this rotation further typically renders such devices incapable of retaining any significant amount of morselized tissue and/or bone fragments, as the centrifugal force generated by such rotation will throw such fragments outward of the wire-bristle fibers.
As a result, an improved specialized tool may be desirable for surgeons and/or surgical technologists for autograft preparation and bone removal, allowing for efficient and effective removal of soft tissue(s) from host bone without removing significant quantities of the bone stock itself.